1. Field of the Invention
The present invention pertains generally to support structures and devices, and more particularly to an agricultural cross arm and trellis apparatus for use in supporting plants, vines or trees which is compatible with mechanical harvesting techniques.
2. Description of the Background Art
Trellis devices have long been used in vineyards and other agricultural operations to support growing vines and plants. Such trellises typically comprise a vertical support with one or more cross arm members affixed to the vertical support. A wire network frequently extends between the cross arms of a series of adjacent trellis structures to provide additional support for plants. Typically, a series of long wires are attached to the cross arm of each trellis within a row of trellises. Wooden trellis structures have long been used in agriculture, but tend to weather and decompose and thus require replacement. In order to overcome this problem, a variety of metal trellises and cross arms have been developed. Metal trellises as used in agriculture have typically employed a conventional metal "T-stake or "roll form" stake as a vertical support member, with a metal cross-arm fastened to the vertical stake. Notches, grooves or slots are usually included adjacent the center of the metal cross arms to facilitate attachment to a vertical T-stake support, and slots of various configuration are included along the cross arms and adjacent the ends of the cross arms to facilitate attachment to wires which run or extend between cross arms along the row of trellises.
The currently known metal cross arm and trellis devices have proved deficient in various respects. Perhaps the greatest drawback of presently available metal trellis structures is inability to withstand the mechanical forces exerted by mechanical harvesting equipment. While grapes and other fruit have traditionally been hand-picked, the use of automated harvesting equipment for such crops is becoming increasingly widespread. The central slots and notches, which are cut into the metal cross arms to facilitate attachment to the vertical T-stake, create a weak point in the cross arm which allows the cross arm to bend or break under the action of mechanical harvesting equipment. The bent or broken cross arms require replacement, and the bending or breaking of the cross arms frequently results in damage to the vine supported thereon.
Another drawback to conventional trellis cross arms is that the action of mechanical harvesters often causes the wires extending between trellises to disengage from the slots provided on the cross arms. The removal of the wires from the cross arms can result in damage to vines supported by the wires, and requires time consuming and labor intensive replacement of the wires. One approach to remedying this problem has been to include bendable metal tabs adjacent the slots for the wires, so that once a wire is inserted in the slot, the tab can be bent into a position to more securely hold the wire within the slot. However, metal cross arms with bent metal tabs cannot be directly manufactured by conventional roll forming techniques, and the bending of the tabs must be carried out subsequent to roll forming via expensive hand labor. Further, the use of such bendable tabs has generally not been effective because employees in the field tend to insert wires into slots on cross arms without bothering to bend the tabs, in order to save time and effort, or do not correctly bend the tabs to retain the wire within the slot.
Accordingly, there is a need for a cross arm apparatus and method for use in trellis structures which is easy to manufacture and is mechanically robust, which can be used for agricultural support structures, which does not undergo bending or breaking under the forces exerted by mechanical harvesting equipment, and which retains attached wires under the forces exerted by mechanical harvesting equipment. The present invention satisfies these needs, as well as others, and generally overcomes the deficiencies found in the background art.